Certain 2-methyl-6-(beta-carbamylethoxy)-benzothiazoles and quaternary salts thereof



United States Patent CERTAIN Z-METHYL 6 (,B-CARBAMYLETHOXYy BIll)I%ZRgTIgIAZOLES AND QUATERNARY SALTS T i O Lester Horwitz, Bronx, and Curt B. Roth, Binghamton,

N.Y., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed May 5, 1958, Ser. No. 732,835

Claims. (Cl. 260-304) This invention relates to 2-methyl-6-(B-carbamylethoxy)-benzothiazoles; the quaternary salts thereof, sensitizing dyes derived therefrom and the silver halide emulsions sensitized with such dyes.

Benzothiazole radicals which are substituted in the 6-position by a hydroxy, methoxy or carboxyethoxy group have already been recommended as intermediates in the preparation of certain cyanine dyes. However, the methods described so far do not provide benzothiazole nuclei in which a carboxamide group is attached to the 6-position of the benzothiazole by means of an ether linkage.

We have now found that extremely valuable sensitizing dyes can be prepared from benzothiazoles which contain a methyl group in the 2-position, a hydrogen atom or methyl group in the 5-position and a carbamylethoxy group in the 6-position. These bases which are readily quaternized by conventional methods can be reacted with cyclammonium quaternary salts containing a reactive group on the a-carbon to produce, inter alia, monoand polymethine cyanine dyes which are valuable sensitizers for silver halide emulsions.

Among the objects of our invention are said bases, their preparation, quaternary salts derived therefrom, sensitizing dyes produced with said quaternary salts, and silver halide emulsions sensitized with said dyes.

The new bases, the preparation and use of which are contemplated herein, are 2-methyl-6-(B-carbarnylethoxy)- benzothiazoles having the following general structure.

wherein R is a hydrogen atom or a methyl group.

These compounds are prepared by the controlled hydrolysis of (,B-cyanoethoxy)-benzothiazole or 2,5-dimeth- 2,984,667 Patented May 16, 1961 yl 6 (fl cyanoethoxy)-benzothiazole. The latter compounds are prepared by reacting the corresponding 6- hydroxy benzothiazoles with acrylonitrile as described in Roth, Horwitz and Levines copending application entitled Z-Methyl 6 3 Cyanoethoxy) -Benzothiazoles as sensitizing Dye Intermediates; Serial No. 724,274, filed March 27, 1958, now Patent No. 2,928,839.

The controlled hydrolysis which is carried out at moderately elevated temperatures, below the boiling point of water, preferably between the range of -80 C., uses concentrated sulfuric or phosphoric acid as the hydrolyzing agent. The reaction is illustrated by the following formulae:

NC-CH2GH2O H+ C-GH3+HaO--- R u HzN-CCHz-OHz-O (3-011, 3- wherein R has the values given above.

The above obtained 6-(,B-carbamylethoxy)-substituted benzothiazole base may be readily quaternized by conventional methods to produce the desired cyclammonium quaternary salts for the cyanine dye synthesis. For instance, the methiodide and the ethiodide are obtained by heating the base with methyl iodide or ethyl iodide, respectively, under pressure in a sealed container for several hours at 96100 C. The quaternary salts obtained are characterized by the following general formula:

wherein R has the value given above; R is alkyl such as methyl, ethyl, propyl, fl-hydroxyethyl, -lhydroxypropyl, allyl and the like; carboxyalkyl, such as carboxymethyl, carboxyethyl, and the like; aralkyl, e.g., benzyl, phenethyl and the like; and X is an anion such as chloride, bromide, iodide, ethylsulfate, perchlorate, p-toluenesulfonate, and the like.

The above quaternary ammonium salts may be converted into sensitizing dyes characterized by the following general formulae:

and

wherein R and R have the values given above; m, n and p represent a positive integer of from 1 to 2; R and R are either hydrogen or a lower alkyl group, e.g., methyl, ethyl, propyl, and the like; R being only hydrogen when n and p equal 1; R represents an alkyl group such as methyl, ethyl, propyl, butyl, amyl; a hydroxy-alkyl group such as hydroxymethyl, hydroxyethyl, hydroxypropyl and the like; carboxyalkyl such as carboxylmethyl, carboxyethyl, carboxypropyl and the like; aralkyl, e.g., benzyl, phenethyl and the like; Y represents an anionic radical, e.g., Cl, Br, I, 010;, SO CH SO C H SO C H CH and the like; and Z represents the hetero atoms necessary to complete a 5- or 6-membered nitrogenous heterocyclic systemv of the type used in cyanine dyes, such as pyridine, lepidine, quinoline, indoline, oxazole, thiazoline, thiazole, selenazole, selenazoline, oxazoline, benzothiazole, benzoselenazole, benzoxazole, naphthothiazole and the like.

These sensitizing dyes are prepared by heating the above 6-(B-carbamylethoxy)-benzothiazolium salts in the presence of an acid binding agent such as pyridine, trimethylamine, triethylamine and the like with a cyclammonium quaternary salt having a reactive grouping on the carbon atom in the 2-position of the heterocyclic ring, for instance, a halogen atom, e.g., chlorine, bromine, or the like, and an alkylmercapto group, e.g., methylmercapto, ethylmercapto, and the like; an alkylmercaptovinyl group, e.g., fi-methylmercaptovinyl, ,B-ethylmercaptovinyl and the like; a B-alkylmercapto-B-alkylvinyl group, e.g., p-methylmercapto-fl-methylvinyl, ,8 ethylmercapto-B-ethylvinyl and the like; fi-acetanilidovinyl, 4-acetanilido, 3- butadienyl, and 6-acetanilido-l,3,5-hexatrienyl.

As examples of suitable cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the 2-position to the nitrogen atom thereof so as to form a monomethine dye, the following may be mentioned:

2-rnethylmercapto-6-methylquinoline ethiodide 2-methylmercapto-6-methoxyquinoline ethiodide 2-methylmercaptopyridine ethiodide Z-methylmercaptothiazoline ethiodide Z-phenylmercaptothiazoline ethiodide, and the like.

In preparing trimethine cyanine dye salts, the following cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the ,B-position of the side chain attached to the carbon atom in the 2-position of the heterocyclic nucleus may be employed:

2- B-acetanilidovinyl -thiazoline ethiodide Z-(fl-acetanilidovinyl)-benzothiazole ethiodide Z-(B-acetanilidovinyl)-benzoxazole ethiodide 2 (,3 ethyl 3 ethylmercaptovinyl) 5 methoxybenzoselenazole ethiodide 2-(B-methylmercapto-/3-methylvinyl)-benzothiazole ethiodide 2-(fl-methylmercapto-fi-propylvinyl)-benzothiazole ethiodide In preparing pentamethine and heptamethine cyanine dyes, the following cyclammonium quaternary salts having a reactive group in the delta-and omega-positions of the side chain attached to the carbon atom in the 2-position of the heterocyclic nucleus may be employed:

2-(4-acetanilido-1,3-butadienyl)-pyridine ethiodide 2-(4-acetanilido-1,3-butadienyl)-benzoxazole ethiodide 2-(4-anilino-3-methyl-1,3-butadienyl)-pyridine ethiodide 2 (4 anilino 3 methyl 1,3 butadienyl) ,3 naphthoxazole ethiodide 2 (4 anilino 3 ethyl 1,3 butadienyl) or naphthothiazole ethiodide 2-(6-anilino-1,3,5-hexatrienyl)-thiazoline ethiodide 2-(6-a'nilino-1,3,S-hexatrienyl)-a-naphthothiazole ethiodide 2 (6 anilino 1,3,5 hexatrienyl) B naphthothiazole ethiodide 2 (6 anilino 1,3,5 hexatrienyl) a naphthoselenazole ethiodide 4 2-(6-anilino-1,3,5-hexatrieny1)-}3-naplhthoselenazo1e ethiodide 2-(6-anilino-4-methyl-1,3,5-hexatrienyl)-thiazoline ethiodide 2 (6 anilino 4 methyl 1,3,5 hexatrienyl) benzothiazole ethiodide 2 (6 anilino 4 butyl 1,3,5 hexatrienyl) benzothiazole ethiodide We have found that our new dyes are especially useful for extending the spectral sensitivity of the customarily employed silver chloride, silver chlorobromide, silver bromide, silver bromoiodide and silver chlorobromoiodide developing out emulsions. The dyes are equally effective in gelatinous emulsions and in those emulsions in which a synthetic colloidal carrier such as modified polyvinyl alcohol is employed.

To prepare emulsions sensitized with one or more of our new dyes, it is only necessary to distribute homogeneously the dye or dyes in the photographic emulsions. The methods of incorporating dyes in emulsions are simple and are well known to those skilled in the art. In practice, it is convenient to add the dyes to the emulsions in the form of a solution in an appropriate solvent. Methanol has proved satisfactory for our new dyes; dimethylformamide or a mixture of acetone and freshly distilled pyridine may also be employed as a solvent. The dyes are advantageously incorporated in the finished, washed emulsions and should be uniformly distributed throughout the emulsions.

The concentrations of dyes in the emulsions can vary widely, e.g., from 5-100 milligrams per liter of flowable emulsion. The concentration of the dyes will vary somewhat according to the type of emulsion and according to the efieot desired.

With most of our dyes, from 15 to 30 milligrams of dye per liter of emulsion (containing about 40 grams of silver halide) sufiice to produce the maximum sensitizing efiiect. With the finer grain emulsions, somewhat larger concentrations of dye may be needed to produce the maximum sensitizing effect.

The new dyes of our invention have been found to be particularly useful since they operate to increase the sensitivity of photographic emulsions containing color formers fast to diffusion to a higher extent than comparable sensitizing dyes without the 6-cyanoethoxy-substituted benzothiazole nucleus. The sensitizing bands of the new dyes of our invention are unusually sharp so that they render themselves advantageously for use in color emul- The invention is further illustrated by the following examples although it is to be understood that the invention is not restricted thereto.

EXAMPLE I 2-methyl-6-(B-cyanoethoxy)-benzothiaz0'le Eight grams (0.05 mole) of 2-methyl-6-hydroxybenzothiazole and 13.3 grams (0.25 mole) of freshly distilled acrylonitrile and 1 milliliter of benzyltrimethylamrnoni u m hydroxide (Triton B) Were heated to reflux on a steam bath for 20 hours. To the hot solution was then added milliliters of benzene and 2 grams of (bone) charcoal. The black slurry was heated to reflux temperature for 10 minutes and then filtered through a Buchner funnel. The charcoal on the filter was extracted with hot benzene and the combined filtrates placed into a separatory funnel. The basic catalyst was removed by washing. The benzene solution was washed with distilled water until the wash water was neutral to Alkacid paper. The benzene layer was then Washed Calculated Found.

can:

soc:

EXAMPLE II Z-m ethyl-fi- ,B-carb amylethoxy) -benzthiazole Ten milliliters of concentrated sulphuric acid and 2.18 grams mole) of 2-methyl(5-cyanoethoxy)-benzothiazole were heated together until the temperature reached 80 C. The clear solution was allowed to stand for five minutes, during which time it cooled down to 70 C. The solution was then poured into 80 milliliters of ice water, and stirred. It was filtered to remove any mechanical impurities and then neutralized by adding, dropwise, a 50 percent aqueous sodium hydroxide solution. After the neutral point (pH 7.0) was reached, 2 milliliters of the 50 percent alkali hydroxide solution were added in excess. The alkali-insoluble 2-methyl-6- (,B-carbamylethoxy)-benzothiazole was filtered off and washed with distilled water until the filtrate was neutral. Traces of 2-methyl-6-(B-carboxyethoxy)-benzothiazole formed by complete hydrolysis of the nitrile remained in the alkaline solution. After drying, 2.31 grams of 2-methyl-6-(p-carbamylethoxy)-benzothiazole having a melting point of 179 -181 C. was obtained.

Analysis for C H 0 N S:

2,5 -dime thyl-6-( fi-carbamylethoxy)-benzothiazole Example 11 is repeated except that the 2.18 grams of G-(B-cyanoethoxy)-2-methylbenzothiazole are replaced by 2.32 grams of 6-(B-cyanoethoxy)-2,5-dimethylbenzothiazole.

EXAMPLE IV 6-(p-carbamylethoxy)-2-methylbenz0thiazole ethiodide Two grams of 2-methyl-6-(B-carbamylethoxy)-benzothiazole and 6 milliliters of ethyl iodide were heated in a sealed container at 'C. for 3 hours. The quaternary salt obtained was filtered from the mother liquor and purified by trituration with acetone, benzene and ether. Yield: l.4 grams; melting point l69171 C.

EXAMPLE V 3- fi-carboxyethyl) -6 fl-carbamylethoxy -2,5-dimethylbenzothiazolium iodide OOH This product is obtained by heating 1.2 grams of 2,5- dimethyl 6 (p carbamylethoxy) benzothiazole and 10 grams of fi-iodopropionic acid in a sealed bomb for 24 hours at 102 C. The resultant product is separated from the mother liquor by filtration, and purified by trituration with ether, ethanol, acetone and again with ether.

EXAMPLE VI 3 -ethyl-6- B-carbamylethoxy -2-methyl'benzolhiaz0lium p-toluene sulfonate E s HaN-O-CI-IaCHz-O- N/C-CH3 02H: 803061146113 EXAMPLE VII 1 ,3-diethyl-6'-methoxy-6-(fi-carbamylethoxy)thiapseudocyanine iodide S\C CHI\UO on; I- N CzHr One hundred fifty-six milligrams (0.4 millimole) of 6- (fl-carbamylethoxy)-2-methylbenzothiazole ethiodide and milligrams (0.4 millirnole) of 2 ethylmercapto 6- methoxyquinoline ethiodide were dispersed in 7 milliliters of methanol. Ten drops of triethylamine were added and the mixture heated on a steam bath to dryness. One milliliter of anhydrous pyridine and 15 milliliters of methanol were added in that order and the mixture heated for 15 minutes on the steam bath. The slurry was centrifuged and the mother liquor discarded. The dye was purified by successive extractions with methanol-benzene (1:14), iso propanol and ether. After drying, 150 milligrams of dye were obtained having a melting point of 179-181" C. The methanol solution had an absorption maximum at 501 millimicrons. This compound sensitized a photographic gelatine silver bromide-iodide emulsion to about 500 millimicrons with a maximum sensitivity at about 480 millimicrons.

iodide emulsion to about "665 millimicrons with the maximum sensitivity at about 645 millimicrons.

EXAMPLE X 6'-(;8-carbamyleth0xy)-3,3',9-triethyZ-S-methoxyselena- EXAMPLE VIII 1 ',3-diezhyl-6'-methyl-6- fi-carbamylethoxy thiapseudocyanine iodide CiHs I This dye was prepared from 156 milligrams of 6-(ficarbamylethoxy)-2-methylbenzothiazole ethiodide and 144 milligrams of Z-ethylmercapto 6 methylquinoline ethiodide following the procedure described in Example VII. The yield was 130 milligrams; the dye melted at 185-187 C. A methanol solution of the dye had an absorption maximum at 487 millimicrons. The dye sensitized a gelatine silver bromide-iodide emulsion to about 500 millimicrons with a sensitivity maximum at 480 millimicrons.

EXAMPLE IX 4 ',5 -b enz0-6- (B-carbamy lethoxy -3,9-d iethyl-3 methy lthiacarbocyanine iodide thiacarbocyanine iodide EXAMPLE XI 3-ethyl-3'-(d-carboxyethyl) -5-methyl-6'-([3-c'arbamyleth0xy)-thiacarb0cyanine iodide Twenty five drops of triethylarnine were added to a solution of 196 milligrams of 3-(fl-carboxyethyD-6-(B- carbamylethoxy)-2,S-dimethylbenzothiazolium iodide and 21-6 milligrams of 2 ([i-acetanilidovinyl)-3-ethylbenzothiazolium iodide in 20 milliliters of ethanol. The prod uct which separated on co'oling was centrifuged and then washed with ethanol, acetone and ether.

EXAMPLE XII One hundred fifty-seven milligrams (0.4 millimole) of 6-(l3-carbamylethoxy) 2 methylbenzothiazole ethiodide and 171 milligrams (0.4 millimole) of 4,5-benzo-2-(fiethyl-[i-methyl-mercaptovinyl) benzothiazole ethiodide were dispersed in 7 milliliters of methanol to which ten drops of triethylamine were then added. The mixture was heated to reflux for 15 minutes on a steam bath. The

slurry was placed into a centrifuge glass and the solid carbocyanine iodide One hundred seventy-five milligrams of 3-ethy-l-6-(ficarbamylethoxy)-2-methylbenzothiazolium p-toluenesulfonate and milligrams of Z-(fl-acetanilidovinyD-3-ethyl- 5,6-dimethyloxazolium iodide were dissolved in 20 milliliters of methanol. Twenty drops of tn'ethylamine were added. The mixture was heated to boiling and then evaporated to dryness on a steam bath. The mixture was successively triturated with ether, isopropanol, acetone and again with ether. The dye melted at 280-282 C. The methanol solution showed an absorption maximum at 530 millimicrons. This dye sensitized a gelatine silver bromide iodide emulsion to about 590 millimicrons with a maximum sensitivity at about 580 millimicrons.

Various modifications of this invention will occur to persons skilled in the art. Thus, our intermediates can O-GH:

2. A sensitizing dye intermediate having the following formula:

3. A sensitizing dye intermediate having the following formula:

C-CHs 4. A sensitizing dye intermediate having the following formula:

EN ('5 on OH 0 C-CH: on, N/

OOH

10 5. A sensitizing dye intermediate selected from the group consisting of those having the following formulae:

O-CH:

and

O-GHa wherein R is a member selected from the group consisting of hydrogen and methyl, R is a member selected from the group consisting of methyl, ethyl, propyl, p-hydroxyethyl, 'y-hydroxypropyl, allyl, carboxyme'thyl, CQIbOXY- ethyl, benzyl and phenethyl, and wherein X is an anion.

References Cited in the file of this patent UNITED STATES PATENTS 2,213,238 Brooker et a1 Sept. 3, 1940 2,231,658 Brooker et a1 Feb. 11, 1941 2,233,873 Rogers et al Mar. 4, 1941 2,395,879 Kendall et al Mar. 5, 1946 2,525,015 Beersmans Oct. 10, 1950 2,610,190 Chao et a1 Sept. 9, 1952 2,715,629 Zwiligmeyer Aug. 16, 1955 OTHER REFERENCES Chemical Abstracts 16, 3101 (Abstracts of Brit. Med. Journal, 1922, I, 514-515.

Chemical Abstracts 19, 530 (Abstract of Proc. Roy. Soc., London, 96 B, 317-33, 1924).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,984,667

May 16, 1961 Lester Horwitz et a1.

It is hereby certified that e ent requiring correction and tha corrected below.

rror appears in the above numbered patthe said Letters Patent should read as Column 6, lines 11 to 20, the formula should appear as shown below instead of as in the patent:

H S H N-C-CH CH -O 2 2 v 2 1:1 /C-CH3 CH3 N/ COOH same column-6-, lines 31 to 38, the formula should appear as shown below instead of as in the patent:

C2H5 so c rl cn Signed and sealed this 24th day of April 1962.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

5. A SENSITIZING DYE INTERMEDIATE SELECTED FROM THE GROUP CONSISTING OF THOSE HAVING THE FOLLOWING FORMULAE: 